複数のテーブルからデータを選択して印刷する

Question

私のケースは基本的にはこれです：itemsforsale、itemsforrent、wanteditemsという3つのテーブルがあります。これらのテーブルのそれぞれは同じ数の列と同じ名前を持ちます。 USERIDが私の選択したIDと等しいこれらの3つのテーブルからすべてのデータを選択して、それらを行として出力したいとします。動いていない。ここに私のコードは次のとおりです。

$sql = "SELECT sale.propertype as propertytype,sale.description as description,sale.price as price,sale.telefone1 as telefone1,sale.telefone2 as telefone2,sale.userid as userid,sale.propertyid as propertyid,sale.area as area,sale.dateposted as dateposted,sale.datebumped as datebumped,sale.images as images,sale.hiddentype as hiddentype,sale.pricetype as pricetype,sale.size as size FROM itemsforsale sale WHERE userid = '1' 
UNION SELECT rent.propertype as propertytype,rent.description as description,rent.price as price,rent.telefone1 as telefone1,rent.telefone2 as telefone2,rent.userid as userid,rent.propertyid as propertyid,rent.area as area,rent.dateposted as dateposted,rent.datebumped as datebumped,rent.images as images,rent.hiddentype as hiddentype,rent.pricetype as pricetype,rent.size as size FROM itemsforrent rent WHERE userid = '1' 
UNION select wanted.propertype as propertytype,wanted.description as description,wanted.price as price,wanted.telefone1 as telefone1,wanted.telefone2 as telefone2,wanted.userid as userid,wanted.propertyid as propertyid,wanted.area as area,wanted.dateposted as dateposted,wanted.datebumped as datebumped,wanted.images as images,wanted.hiddentype as hiddentype,wanted.pricetype as pricetype,wanted.size as size from itemswanted wanted WHERE userid = '1'"; 
$result = mysqli_query($mysqli, $sql); 

エラー： 警告：mysqli_fetch_array（）私はそれが正常に動作しない場合はブール値がライン290

にblahblahで与えられ、パラメータ1がmysqli_resultことを期待しています。どんな助け？

Answer 1

SELECT *とUNIONを使用することはできません。列名を指定する必要があります。ドキュメントが言うHere年代：

The column names from the first SELECT statement are used as the column names for the results returned. Selected columns listed in corresponding positions of each SELECT statement should have the same data type. (For example, the first column selected by the first statement should have the same type as the first column selected by the other statements.)

はまた、注文を適用するには、UNIONクエリのORDER BY外を使用する必要があります。

To apply ORDER BY or LIMIT to an individual SELECT, place the clause inside the parentheses that enclose the SELECT